1. Field of the Invention
Present invention relates to an obstacle sensing apparatus mounted on a vehicle to avoid accidents, e.g., collisions and, more particularly, to an obstacle sensing apparatus for sensing the distance between the vehicle and an obstacle in front of the vehicle.
2. Description of the Related Art
Japanese Patent Application Laid-Open (Kokai) No. 2-287180 presents a scanning-type radar unit, which transmits radar waves such as optical waves and radio waves forward, and receives the radar waves reflected from an obstacle in front of the vehicle such as a vehicle running ahead. The distance between the vehicle and the obstacle and the direction from the obstacle to the vehicle are predicted by measuring a time period between the transmitting point and the receiving point. If the radar unit transmits radar waves within a comparatively wide range in front of the vehicle, the radar unit detects an obstacle even upon quick turning of the vehicle body. However, as the sensing covers such wide range, a large amount of unnecessary information intrudes in the radar unit. This prolongs measurement to specify obstacles of highest danger level. Since the sensing of obstacles cannot be made efficiently, problems may occur when judging the possibility of encounter with the obstacle.
To solve the above drawback, Japanese Patent Publication (Kokoku) No. 51-7892 provides an obstacle sensing apparatus comprising traveling-path predicting means for predicting a path on which the vehicle will travel, based on the running state of the vehicle indicated by the steering angle, the velocity, etc. The obstacle sensing device picks up only information within a range which covers the traveling-path predicted by the traveling-path predicting means, included in the obstacle information obtained from wide-range sensing by a radar unit.
Assuming that this conventional obstacle sensing apparatus performs traveling-path prediction, at a point where the road changes from a straight road to a curved road, the predicted traveling-path will not coincide with the actual road. This may cause erroneous obstacle sensing. For example, the guardrail of the road may be recognized as an obstacle.